Thanks for contributions. And especially Brumby for the info on how they calculate the Zip. Always wondered. But I have found the Zip a good guide. Often you can spend hours rating horses and come up with much the same results as the Zip analysts. I read of an analyst, looking at 2 years of results, who found the Zip star the second most reliable guide to a winner (after both best av. prize/av.places horses). Useful. As explained above I've been using it to select races. I also avoid races where two horses get the zip star. Again, if the zip analysts can't separate them, how can I?